sort and collect data

Hi Guys, I have file that looks like this below (20 x 4) matrix. It consists of time, serial number, pessure and volume. I want to select the maximum value of pressure and the corresponding volume and time for each serial numbers every 4 secs all through the data. There are 4 items, serial number 1 represents the first, 2 the second, e.t.c. However the serial number 1 represents time where there is low/ no pressure as well. Could you help with this? Thanks

Time	S/N	Pressure 	Volume
00:00:01	1	20	2.4
00:00:02	1	25	2.5
00:00:03	1	30	2.6
00:00:04	1	35	2.7
00:00:05	1	0.3	2.8
00:00:06	1	1.4	2.9
00:00:07	2	20	3
00:00:08	2	30	3.1
00:00:09	2	40	3.2
00:00:10	2	50	3.3
00:00:11	1	0.6	3.4
00:00:12	1	1.5	3.5
00:00:13	3	20	3.6
00:00:14	3	30	3.7
00:00:15	3	40	3.8
00:00:16	3	50	3.9
00:00:17	1	0.1	4
00:00:18	1	2.3	4.1
00:00:19	4	20	4.2
00:00:20	4	30	4.3
00:00:21	4	34	4.4
00:00:22	4	50	4.5
00:00:23	1	0.3	4.6
00:00:24	1	4.1	4.7

[Adam Danz]

Are there always 6 samples of each S/N and is S/N always in ascending order (except for the low pressure indicators)?

[Olu B]

There are always 4 samples of each S/N that represents every 4 seconds and the S/N is always in ascending order except for the low pressure indicators that represents 2 secs of low/no pressure, that is why I have more 1's showing up than other S/N. The program is suppose to take measurement every 4 secs and 2 secs no measurement so as to differentiate the 4 S/N however when there is no/low pressure for those 2 secs time step it is being logged as S/N 1

Answer 1

[Adam Danz]

Assuming you have 3 vectors named sn, pressure, and volume,

% Replace every 5th and 6th sn with 0
% * assumes that there will always be 4 samples of each SN
%   followed by 2 low-pressure
sn(repmat(logical([0;0;0;0;1;1]),numel(sn)/6,1)) = 0;

% Identify groups of sn
[snGroupIdx, snGroup] = findgroups(sn); 

% Calculate the max pressure within each group
maxPresSn = splitapply(@max,pressure,snGroupIdx); 

% Find the volume that corresponds to the max pressure in each group
volumnSn = splitapply(@(x1,x2)x2(find(x1==max(x1),1)),pressure,volume,snGroupIdx); 

% Put the results in a summary table
t = table(snGroup, maxPresSn, volumnSn, 'VariableNames', {'SN','MaxPres','Vol'});

Result

t =  % FAKE DATA
  5×3 table
    SN    MaxPres    Vol
    __    _______    ___
    0       32        1 
    1       19        1 
    2       37        3 
    3       30        3 
    4       13        1 

[Olu B]

Thanks Adam.

[Adam Danz]

Glad I could help!